1. Field of the Invention
The present invention relates to a method to perform a cycle synchronization between interconnected sub-networks and a cycle synchronizator adapted to perform said method.
2. Discussion of the Background
It is known to interconnect sub-networks, e.g. with long delay bi-directional connections to extend a network to a wider area. In particular, this technique is used to interconnect several IEEE 1394 serial buses to extend an IEEE 1394 network, e.g. through a whole house. The basic topology of such a connection is shown in FIG. 1. A first interface 20 is part of a first IEEE 1394 serial bus 21 which might consist of a number of IEEE 1394 nodes. A second interface 22 is part of a second IEEE 1394 serial bus 23 which might comprise another number of IEEE 1394 nodes. The first interface 21 and the second interface 22 are connected via a long delay bi-directional connection 24 which might be, but is not restricted to a coax cable medium.
Independent IEEE 1394 buses must be synchronized to have the same cycle rate. In particular, the IEEE 1394 standard mandates that for opened isochronous channels an isochronous packet is sent in every isochronous cycle. To ensure that isochronous transfers between the interconnected IEEE 1394 buses work, it must be ensured that all buses have the same frequency of isochronous cycles.